Turning a complex 3d object into a 2d contour
One possible way to achieve this is by acquiring a "skeleton" of your mesh. This is a destructive process, if you require the original mesh intact make these steps in a copy of the original.

In Edit Mode erase all faces but leaving edges by pressing X > Only Faces option.

Optionally Scale you object to zero in the desired axis or custom direction (if you don't want any of the orthogonal axis).

Add a new plane or flat mesh to your scene aligned with the desired projection direction, in such way that it stays behind the mesh you want to outline.

Select the outlining mesh, then Shif-select the plane object so it becomes the active object, while still leaving the outlining mesh selected.

Align the view to the desired projection direction, also ake sure you have a orthographic projection view (as opposed to perspective) this is important as it will determine the accuracy of the obtained outline scale and size. Enter Edit Mode in the plane object, then use Knife Project operator from the space bar menu to "imprint" the mesh onto the plane.

Select the major faces surrounding your newly obtained outline, press Ctrl + i to invert the selection and erase everything else.

You now have an outline of your mesh. Do some cleanup, like Remove Doubles and convert to a curve if that is what you desire.



Optionally try the SVG Output script for direct to vector exporting.